Thermally stable dyeable polyesters having improved dyed lightfastness

ABSTRACT

Modified polyester filaments having over conventional polyester filaments, improved inherent thermal stability in the presence of oxygen and inherent disperse dye uptake, without the significant loss in dye lightfastness typical of such modified filaments, are produced from terephthalic acid; glycols; small amounts of mixtures of compounds having a typical general formula: R-O(GO)x-H, where R is an alkyl group containing an average of from about 8-20 carbon atoms; G is a hydrocarbon radical selected from the group consisting of ethylene, propylene and isomers thereof, butylene and isomers thereof, and mixtures of the above; and x has an average value of from 8-20, and is about equal to or greater than R; small amounts of manganous ion; and small amounts of a hindered phenol preferably selected from the group consisting of 4, 4&#39;&#39;-butylidenebis (6-t-butyl-m-cresol) and 2, 2&#39;&#39;butylidenebis (6-t-butyl-m-cresol). Polyfunctional chainbranching agents in amounts up to about 0.7 mole percent, based on the weight of the dicarboxylic acid or ester-forming derivative thereof, may be added, whereby the polymer, with the chain terminators described above, can be polymerized to higher molecular weights by ordinary polymerization techniques.

United States Patent King et al. 51 *June 13, 1972 [54] THERMALLY STABLEDYEABLE 3,223,752 12/1965 Tate et al ..260/873 POLYESTERS HAVINGIMPROVED 3,461,468 8/1969 Morgan et al. ..260/75 T DYED LIGHTFASTNESSInventors: Henry L. King; Eugene L. Ringwald, both of Cary, NC; James C.Randal], Jr., Bartlesville, Okla.

Assignee: Monsanto Company, St. Louis, Mo.

Notice: The portion of the term of this patent subsequent to June 6,1989, has been disclaimed.

Filed: April 28, 1970 Appl. No.: 32,676

Related US. Application Data Continuation-in-part of Ser. No. 824,092,May 13, 1969, and a continuation-in-part of Ser. No. 789,528, Jan. 7,1969, abandoned, and a continuation-in-part of Ser. No. 873,333, Nov.13, 1969.

References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONSJapan Japan [5 7] ABSTRACT Modified polyester filaments having overconventional polyester filaments, improved inherent thermal stability inthe presence of oxygen and inherent disperse dye uptake, without thesignificant loss in dye lightfastness typical of such modifiedfilaments, are produced from terephthalic acid; glycols; small amountsof mixtures of compounds having a typical general formula: R-O[G-O],H,where R is an alkyl group containing an average of from about 8-20carbon atoms; G is a hydrocarbon radical selected from the groupconsisting of ethylene, propylene and isomers thereof, butylene andisomers thereof, and mixtures of the above; and x has an average valueof from 8-20, and is about equal to or greater than R; small amounts ofmanganous ion; and small amounts of a hindered phenol preferablyselected from the group consisting of 4, 4-buty- Iidenebis(6-t-butyl-m-cresol) and 2, 2-butylidenebis (6-tbutyl-mcresol).Polyfunctional chain-branching agents in amounts up to about 0.7 molepercent, based on the weight of the dicarboxylic acid or ester-formingderivative thereof, may be added, whereby the polymer, with the chainterminators described above, can be polymerized to higher molecularweights by ordinary polymerization techniques 9 Claims, 3 DrawingFigures PKTENTEDJux I 3 m2 3. 669.92 5

MICRO MOLES OF HCHO I O 5 IO I5 20 25 3O -N0.0F E O UNITS LOSS OFFORMALDEHYDE OF VARIOUS ETHYLENE OXIDE POLYETHERS LIJ O o 2 4 e elOl2l4l6l82O DISPERSE DYEABILITY AS A FUNCTION OFR LIJ 5 o 4 a 12I620242832 DISPERSE DYEABILITY ASA FUNCTION OF x 'NVENTORS HENRY L. KINGFIG 3 EUGENE L. RINGWALD J ES C. RANDALL BY %Z ZZ 7 TTORNE THERMALLYSTABLE DYEABLE POLYESTERS HAVING IMPROVED DYED LIGHTFASTNESS This is aconfinuation-in-part application of our co-pending applications Ser. No.824,092, filed May 13, 1969; Ser. No. 789,528, filed Jan. 7, 1969 andnow abandoned; and Ser. No. 873,333,filed Nov. 13, 1969.

BACKGROUND OF THE INVENTION This invention relates to polyestersproduced by condensation reactions of polymethylene glycols anddicarboxylic acids or reactive derivatives thereof. It is well knownthat some polymeric polyesters prepared by the condensation of a glycolor its functional derivatives and a dicarboxylic acid or apolyester-forming derivative thereof, such as an acid halide, a salt, ora simple ester of a dibasic acid and volatile monohydric acid areexcellent fiber-forming polymers. Commercially, high polymericpolyesters are prepared, for example by the condensation of terephthalicacid of dimethyl terephthalate and a polymethylene glycol containingfrom about two to carbon atoms. These polyesters are relativelyinsoluble, chemically inactive, hydrophobic materials capable of beingformed into filaments which can be cold-drawn to produce textile fibersof superior strength and pliability. However, since these materials arenot readily permeable to water, they cannot be satisfactorily dyed byordinary dyeing procedures.

The compact structure of polyethylene terephthalate fibers, for example,the molecules of which are closely packed along the axis of the fibers,makes it quite difficult, except with a limited number of dyes, toobtain a high degree of dyebath exhaustion or to secure satisfactorydeep shades. Absorption and penetration of the dye into the fiber coreare limited by the inherent properties of the fiber.

A number of methods have been proposed to increase the dyeability ofpolyesters, and particularly polyethylene terephthalate; however, mosthave not proved to be entirely satisfactory. These methods have includedthe use of a number of additives to the polyester and variouscombinations of drawing and heat-treatment steps and procedures.Unfortunately, the use of most of these known procedures has resulted inthermally unstable polyesters, deterioration in fiber properties,nonuniformly dyed polymers, and the like. Finally, the art has desiredsome other means to produce thermally stable polyesters having improveddyeability. Thermally stable polyesters having improved dyeability wouldhave significant commercial and practical value and utility.

Our co-pending application Ser. No. 824,092, filed May 13, 1969describes the use of small amounts of compounds having a typical generalformula: RO[G-O],.H where R is an alkyl group containing an average offrom about 8-20 carbon atoms; G is a hydrocarbon radical selected fromthe group consisting of ethylene, polypropylene and isomers thereof,butylene and isomers thereof, and mixtures of the above; and x has anaverage value of from 8-20, and is about equal to or greater than R.These modified polyester compositions are prepared by reacting anaromatic dicarboxylic acid, the polymethylene glycol and a small amountof the glycol additive under polyesterification conditions until afiber-forming polymeric polyester composition is obtained. Small amountsof a chain-branching agent may also be added to the reaction as desired.These modified polyester compositions are useful in the production ofshaped articles by extrusion, molding, or casting in the nature ofyarns, fabrics, films, pellicles, bearings, ornaments, or the like. Theyare particularly useful in the production of thermally stable textilefibers having improved dyeability, particularly with disperse dyes. Onedifiiculty encountered in the use of such modified polyesters lies inthe fact that the substrate alone, as well as the dyed substrate has aninferior lightfastness as compared with a filament comprised ofsubstantially unmodified polyester filament produced under otherwisesimilar conditions.

Theoretically, this inferior lightfastness occurs by way of absorptionof energy at the site in the polymer where spectral characteristics canbe slightly modified by a fiber morphology,

e.g., the site of the glycol additive. This energy is then transferredto oxygen and possible water molecules resulting in the formation ofperoxides. This hydroperoxide formation in the polymer is primarilydependent upon the glycol additive, although to a lesser extent, anydiethylene glycol present, ultimately leads to oxidative degradation ofthe dye molecules.

In our co-pending application Ser. No. 873,333, a process for theimprovement of lighfiastness qualities in the type of modified polyesterdescribed in our co-pending application Ser. No. 824,092, was described.This process involved the use of small amounts of manganous ion whichwas believed to act as a quencher" for the excited triplet state of dyemolecules in order to prevent dye degradation; at the same time tendingto stabilize the polymer substrate, or the alkoxy glycol additiveportion thereof, so that heat stability, maintenance of strength, andwhiteness of the substrate is also improved.

SUMMARY OF TI-IE INVENTION It is an object of this invention to providea modified polyester filament having the inherent superior thermalstability in oxygen or air and disperse dye uptake characteristic of themodified polyesters described in our co-pending application Ser. No.824,092, filed May 13, 1969, at the same time having a further improveddyed lightfastness and a satisfactory substrate undyed lightfastness.

It is another object of this invention to provide a process for thepreparation of modified polyester filaments consisting of at least aboutpercent by weight of an ester of a dihydric alcohol and terephthalicacid with improved lightfastness, both dyes and undyed, as well as theinherent superior thermal stability in oxygen and disperse dye uptakecharacteristics of these modified polyester filaments.

Briefly, the objects of this invention are accomplished by preparing afiber-forming polyester from a dicarboxylic acid and a glycol andcontaining in the polymer molecule a small amount of compounds having atypical general formula: R- O[GO],H, where R is an alkyl groupcontaining an average of from about 8-20 carbon atoms; G is ahydrocarbon radical selected from the group consisting of ethylene,propylene and isomers thereof, butylene and isomers thereof, andmixtures of the above; and x has an average value of from 8-20, and isabout equal to or greater than R. Mixtures of these glycols may also beused. The alkoxy glycol additive may be used at concentrations ofbetween about 0.25 and 3 mole percent, based on the weight of thedicarboxylic acid or esterforming derivative thereof or on eachpolyester repeating unit. Preferably, the alkoxy glycol additive ispresent in an amount of from about 0.75 to 2 mole percent, based on theweight of the dicarboxylic acid or ester-forming derivative thereof oron each polyester repeating unit. The use of less than 0.25 mole percentof the alkoxy glycol additive does not give significant improvement inthe dyeability in the final product, and when more than 3 mole percentof the additive is employed, undesirable quantities of chain-branchingagents are necessary to counteract the tendency of the monohydroxyladditive to restrict the buildup of molecular weight in the finalpolymeric product. In addition to the alkoxy glycol additive, smallamounts of manganous ion are added in the form of a salt which isbelieved to act as a quencher for the excited triplet state of dyemolecules in order to prevent dye degradation; and to stabilize thepolymer substrate, or the alkoxy glycol additive portion thereof, sothat heat stability, maintenance of strength, and whiteness of thesubstrate are also improved. Further, in addition to the alkoxy glycoladditive and small amounts of the manganous ion, a small amount of ahindered phenol, preferably selected from the group consisting of 4, 4,4, 4-butylidenebis(-t-butyl-m-cresol) and 2,2-butylidenebis(6-t-butyl-m-cresol) and the like, is also added to prevent dyedegradation by oxidation.

To further understand the invention, reference will be made to theattached drawings that form a part of the present invention:

FIG. 1 is a graph showing the amount of formaldehyde loss at 195 C. for60 minutes of alkoxy polyethylene glycols varying in the number ofethylene oxide units present in the molecules;

FIG. 2 is a graph showing the relative disperse dyeability in terms ofpercentage of the dye, based on the weight of the fiber, of polyesterfibers modified with alkoxy polyethylene glycols in which the carbonatoms in the alkoxy group represented by R in the general formula, wasvaried between four and 20, with the number of ethylene oxide units (x)constant at a value of 12-14; and

FIG. 3 is a graph showing the relative disperse dyeability in terms ofpercentage of dye on the weight of the fiber, of polyester fibersmodified with an alkoxy polyethylene glycol in which the number ofethylene oxide units (x) was varied from between four and 30, with Rconstant at a value of from l2l4.

Other objects and advantages of this invention will be apparent from thedescription which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The synthetic linearcondensation polyesters contemplated in the practice of the inventionare those formed from dicarboxylic acids and glycols, and copolyestersor modifications of these polyesters and copolyesters. In a highlypolymerized condition, these polyesters and copolyesters can be formedinto filaments and the like and subsequently oriented permanently bydrawing. Among the polyesters and copolyesters specifically useful inthe instant invention are those resulting from heating one or more ofthe glycols of the series HO(CH ),,OH, in which n is an integer from 2to 10, or cycloaliphatic glycols, with one or more dicarboxylic acids,or ester-forming derivatives thereof. Among the dicarboxylic acids andester-forming derivatives thereof useful in the present invention theremay be named terephthalic acid, isophthalic acid, p,p-dicarboxybiphenyl,p, p-dicarboxydiphenylsulfone, p,p-dicarboxydiphenylmethane, and thealiphatic, cycloalphatic, and aryl esters and half-esters, ammonium andamine salts, and the acid halides of the abovenamed compounds, and thelike. Examples of the polyhydric alcohols which may be employed inpracticing the instant invention are ethylene glycol, trimethyleneglycol, tetramethylene glycol, and cyclohexane dimethanol, and the like.Polyethylene terephthalate, however, is the preferred polymer because ofthe ready availability of terephthalic acid or dimethyl terephthalateand ethylene glycol, from which it is made. It also has a relativelyhigh melting point of about 250 through 265 C., and this property isparticularly desirable in the manufacture of filaments in the textileindustry.

Additives which are an essential part of this invention includecompounds having a typical general formula: RO[G- O],H, where R is analkyl group containing an average of from about 8-20 carbon atoms; G isa hydrocarbon radical selected from the group consisting of ethylene,propylene and isomers thereof, butylene and isomers thereof, andmixtures of the above; and x has an average value of from 8-20 and isabout equal to or greater than R. By average" is meant that the alkoxyglycol additive may comprise mixtures of the alkoxy glycol with somevariances from the figures shown; but that the average of the integersin the mixture will be as indicated. Preferably, the R group contains12-16 carbon atoms. The optimum degree of polymerization (x) is aboutl2l 6. This additive may be used at concentrations of from about 0.25 to3 mole percent, based on the weight of the dicarboxylic acid orester-forming derivative thereof or on each polyester repeating unit.Preferably, the additive is present in amounts of from about 0.75 to 2mole percent, based on the weight of the dicarboxylic acid orester-forming derivative thereof or on each polyester repeating unit.

Autoxidation is the phenomenon which is responsible for much of ourenvironmental chemistry. It is involved in the aging of fats and oils,drying of paints, and degradation of natural and synthetic fibers. Theprocesses involved may be catalyzed by heat or light and are freeradical by nature. Generally speaking, autoxidation proceeds by freeradical, chain mechanisms; peroxy radicals and hydroperoxide groups areformed which are precursors to other products. Typical products fromautoxidation processes are alcohols and carbonyl-containing compounds.Chain-terminating reactions significantly afiect the rates ofautoxidation processes.

The products observed from the autoxidation of alkoxy polyethyleneglycols are principally alcohol and fonnate ester chain-terminal groupsand formaldehyde, carbon dioxide, and water. Formaldehyde is a majorvolatile product. As above stated, significant and surprisingdifferences in thermal stability in the presence of oxygen have beenobserved among the various alkoxy polyethylene glycols. The type ofalkoxy unit and the degree of polymerization are apparently related tothe susceptibility of autoxidation.

It has been found, for example, that as the number of carbon atoms inthe alkoxy end group (R) is increased beyond the methoxy (with degree ofpolymerization held constant) there is a surprising degree in the amountof formaldehyde evolved when the glycol additive is heated in a sweep ofair at 193 C., until the alkoxy group reaches eight carbon atoms, afterwhich there is a leveling off. Further increase beyond 8-l4 carbon atomsin the alkoxy group causes no appreciable difierences in the heatstability of the glycol. Exemplifying the above, alkoxy terminatedpolyethylene glycol polymers having the structural formula: R(OCH CH -OHwere subjected to the above-described conditions, and liberatedformaldehyde in accordance with the following table.

alkoxy polyethylene glycol prepared from mixture of 14 and 15 carbonalcohols.

It was also discovered that when these same alkoxy glycols were used aschain terminators in the production of modified polyesters, the heatstability effect was carried over to the polyester fiber.

On the other hand, where the number of carbon atoms in the alkoxy endgroup was held constant at about 14 and the degree of polymerization ofthe polyether chain was increased, the compounds being heated in a sweepof air at 195 C., for 60 minutes, there was a marked increase in thenumber of micromoles of formaldehyde released as the degree ofpolymerization (number of ethylene oxide units) was increased from about5 to 30, indicating a decrease in heat stability of the alkoxy glycol asshown by FIG. 1. Therefore, so far as heat stability alone is concerned,and ignoring any possible efiect of the relationship of the degree ofpolymerization to the length of the alkoxy end groups, it appears thatan alkoxy poly(oxyalkylene) glycol as described above where R is analkyl group containing no less than eight carbon atoms, and with anextremely low degree of polymerization would be optimum.

As stated above, however, dyeability of the modified polymer is anextremely important factor so far as the use of these additives isconcerned. In FIG. 2, the effect on fiber dyeability of changes in thenumber of carbon atoms in the alkoxy group (R) with the degree ofpolymerization (x) being held constant at 11-13 is shown; and in FIG. 3,the effect of changes in the degree of polymerization (x) with R beingheld constant at 14.5 is shown, FIGS. 2 and 3 show the dispersedyeability of these compounds in terms of percent dye on the weight ofthe fiber, dyeing being accomplished as explained in Example 1. It willbe observed from FIG. 2 that there is a tendency toward decreaseddyeability as the number of carbon atoms in the alkoxy end group of theadditive increased. FIG. 3 shows a substantial increase in dyeability asthe degree of polymerization (x) is increased from about 4 to about12-14, and thereafter a decrease in dyeability.

A minimum optimum value of 8 representing the number of carbon atoms inthe alkoxy end groups has thus been established on the basis of heatstability, and a maximal optimum value of 20 has been established beyondwhich there is no substantial increase in heat stability, but there is acorresponding decrease in disperse dyeability (FIG. 2).

The degree of polymerization has been established on the basis ofdyeability with about 8 as a minimally marginal value and 20 as amarginally maximum value (FIG. 3), with decreasing heat stability acrossthe range (FIG. 2). An additional limiting factor involving therelationship of R to x will be developed in the examples.

The precise structure of G is not considered critical in that theinstant invention except insofar as it must exclude the alkoxy(polyoxymethylene) glycols which depolymerize under polyesterpolymerization conditions. We have found that the alkoxypoly(oxyethylene), alkoxy poly( oxypropylene), and alkoxypoly(oxytetramethylene) glycols (including copolymers and blockcopolymers) and mixtures thereof produce good results in accordance withthis invention.

The above can be partially explained in terms of inhibition of furtherautoxidation by products formed from the terminal alkoxy groups in theinitial stage of oxidation. Those derived from short alkyl chains arevolatile at the test temperature, and escape without acting asinhibitors.

When the additive contains an alkoxy group which is an effectiveinhibitor of autoxidation, the number of alkyleneoxy units in thepolyether additive becomes significant. It has been found that chainshaving more than about 25 units are not adequately stable. This isbelieved to result from the low concentration of the inhibiting terminalalkoxy group in such a chain. On the other hand, a low number ofalkyleneoxy units per molecule results in an excessive number of chainterminations when an adequate weight of the modifier is added to achievethe desired dyeability. Poor processability results from excessive chaintermination.

Since the hydrophobic alkyl portion of the additive makes very little,if any, contribution to the enhanced dyeability, it is desirable that amajor portion of the molecule be comprised of the hydrophilic polyetherchain. Thus, alkoxy poly(oxyalkylene) glycols in which the number ofoxyalkylene groups is about equal to or greater than the number ofcarbon atoms in the alkyl group, resulting in a polymer composed of morethan seventy percent by weight of the hydrophilic polyether portion, aswill be shown in the examples, are most effective (see Table III).Included within the meaning of about equal, as used herein, is :2.

The second additive to the polymerization mix is the manganous ion inthe form of a salt such as acetate, formate, terephthalate, succinate,and adipate. It has been found that in amounts of 10-500 parts permillion of Mn ion and preferably 50-150 parts per million of Mn, basedon the weight of the acid and glycol, dyed lightfastness in the filamentproduct is substantially improved. Where amounts are used in excess ofabout 200-300 ppm, the product may be somewhat colored by the additive.It has been found that 50-150 parts per mil lion of a hindered phenolpreferably selected from the group consisting of 4, 4'-butylidenebis(6-t-butyl-m-cresol) and 2,2- butylidenebis (G-t-butyl-m-cresol),further improves dyed lightfastness in the filament. Other hinderedphenols known to function in a similar manner include the followingcompounds which are available commercially and known as antioxidants:

CH: 0 H

This improvement is found only when the hindered phenol is used incombination with the manganous ion. Where the hindered phenol is usedalone, there is no significant improvement in dyed lightfastness oversamples containing neither the manganous ion nor the hindered phenol.This would suggest that there is a synergistic action between themanganous ion and the hindered phenol; however this is only a theory.The hindered phenol, in any event, is believed to act as an anti-oxidantand will prevent dye degradation by oxidation.

If desired, the modified polyesters of this invention may containchain-branching agents, which, as taught in U.S. Pat. No. 2,895,946, areemployed to increase the viscosity or molecular weight of thepolyesters, such as polyols which have a functionality greater than two;that is, they contain more than two functional groups, such as hydroxyl.Examples of suitable compounds are pentaerythritol; compounds having theformula: R(OI-I) wherein R is an alkylene group containing from three tosix carbon atoms, for example, trimethylol ethane, trimethylol propane,and the like compounds up to trimethylol hexane; and the compoundshaving the formula:

where n is an integer from I to 6. As examples of compounds having theabove formula, there may be named 1,3,5- trimethylol benzene;l,3,5-triethylol benezene; 1,3,5- tripropylol benezene; 1,3,5-tributylolbenzene; and the like.

Aromatic polyfunctional acids or their esters may also be employed inthis invention as chain-branching agents, and particularly those havingthe formula:

l (EM).

and in which R is H or an alkyl group containing one to three carbonatoms and x is an integer of 3 or 4. As examples of compounds having theabove formula, there may be named trimesic acid, trimethyl trimesate,and tetramethyl pyromellitate, and the like. In addition, there may beemployed mixtures of the above acids and esters which are obtained inpractical synthesis. That is, in most instances, when preparing any ofthe compounds having the above formula, other related compounds havingthe same formula may be present in small amounts as impurities. Thisdoes not affect the compound as a chain-branching agent in thepreparation of the modified polyesters and copolyesters describedherein.

The chain-branching agents may be employed in the preparation of thepolyester and copolyesters in amounts ranging from 0 mole percent to 0.7mole percent, based on the amount of dicarboxylic acid or ester-formingderivative thereof employed in the reaction mixture. If thechainbranching agent is tetrafunctional, as for example,pentaerythritol, quantities not in excess of 0.45 mole percent should beused. The preferred concentration of a tetra-functional chain-branchingagent is about 0.2 mole percent. If a tri-functional chain-branchingagent, such as for example, trimesic acid, is used, somewhat more isrequired for results equivalent to that of the tetra-functionalchain-branching agent, and amounts up to 0.7 mole percent may be used.The preferred concentration of a tri-functional chain-branching agent is0.5 mole percent.

In the practice of this invention, the dibasic acid or esterformingderivative thereof, the glycol, and alkoxylpolyoxylalkylene glycol, themanganese salt and the hindered phenol are charged to the reactionvessel at the beginning of the first stage of the esterificationreaction, and the reaction proceeds as in well-known esterificationpolymerization. If desired, the chain-branching agent may also becharged to the reaction vessel at this time.

When preparing the polyester from an ester, such as dimethylterephthalate, the first stage of reaction may be carried out at to C.and at a pressure ofO to 7 p.s.i.g. If the polyester is prepared fromthe acid, such as terephthalic acid, the first stage of reaction may becarried out at about 220 to 260 C. and at pressures of from atmosphericto about 60 p.s.i.g. The methanol or water evolved during the firststage of reaction is continuously removed by distillation. At thecompletion of the first stage, the excess glycol, if any, is distilledoff prior to entering the second stage of the reaction.

In the second or polymerization stage, the reaction may be conducted atreduced pressures and preferably in the presence of an inert gas, suchas nitrogen, in order to prevent oxidation. This can be accomplished bymaintaining a nitrogen blanket over the reactants, the blanketcontaining less than 0.033 percent oxygen. For optimum results, apressure within the range of less than 1 mm. up to 5 mm. of mercury isemployed. This reduced pressure is necessary to remove the free ethyleneglycol that is formed during this stage of the reaction, the ethyleneglycol being volatilized under these conditions and removed from thesystem. The polymerization step is conducted at a temperature in therange of 220 to 300 C. This stage of the reaction may be effected eitherin the liquid melt or solid phase. In the liquid phase, particularly,reduced pressures must be employed in order to remove the free ethyleneglycol which emerges from the polymer as a result of the condensationreaction.

Although the process of this invention may be conducted stepwise, it isparticularly adaptable for use in the continuous production ofpolyesters. In the preparation of the described polyesters, the firststage of the reaction takes place in approximately three-fourths to 2hours. The use of an ester-interchange catalyst is desirable whenstarting with dimethyl terephthalate. In the absence of a catalyst,times up to 6 hours may be necessary in order to complete this phase ofthe reaction. In the polymerization stage, a reaction time ofapproximately 1 to 4 hours may be employed with a time of l to 3 hoursbeing the optimum, depending on catalyst concentration, temperature,viscosity desired, and the like.

The linear condensation polyesters, produced in accordance with thepresent invention, have specific viscosities in the order of about 0.25to 0.6, which represent the fiberand filament-forming polymers. It is tobe understood, of course, that nonfiber-forming polyesters may beproduced by means of the present invention, which have a greater or lessmelt viscosity than that specified above.

Specific viscosity, as employed herein, is represented by the formula:

Time of flow of the solvent in seconds Viscosity determinations of thepolymer solutions and solvent are made by allowing said solutions andsolvent to flow by force of gravity at about 25 C. through a capillaryviscosity tube. In all determinations of the polymer solutionviscosities, a solution containing 0.5 percent by weight of the polymerdissolved in a solvent mixture containing two parts by weight of phenoland one part by weight of 2,4,6-trichlorophenol, based on the totalweight of the mixture is employed.

The polyesters of this invention may be produced to form filaments andfilms by melt-spinning methods and can be extruded or drawn in themolten state to yield products that can be subsequently cold-drawn tothe extent of several hundred percent of their original lengths, wherebymolecularly oriented structures of high tenacity may be obtained. Thecondensation product can be cooled and comminuted followed by subsequentremelting and processing to form filaments, films, molded articles, andthe like.

Alternatively, the polyesters of this invention may be processed toshaped objects by the wet-spinning method, wherein the polyesters aredissolved in a suitable solvent and the resulting solution is extrudedthrough a spinnerette into a bath composed of a liquid that will extractthe solvent from the solution. As a result of this extraction, thepolyester is coagulated into filamentary material. The coagulatedmaterial is withdrawn from the bath and is then generally subjected to astretching operation in order to increase the tenacity to inducemolecular orientation therein. Other treating and processing steps maybe given the oriented filaments.

If it is desired to produce shaped articles from the polyesters of thepresent invention which have a modified appearance or modifiedproperties, various agents may be added to the polyester prior to thefabrication of the articles or those agents may be incorporated with theinitial reactants. Such added agents might be plasticizers, antistaticagents, fire-retarding agents, stabilizers, and the like.

To further illustrate the present invention and the advantages thereof,the following specific examples are given, it being understood thatthese are merely intended to be illustrative and not limitative. Unlessotherwise indicated, all parts and percents are by weight.

The following procedure was used to prepare the polymers in theexamples. The charge was added directly to a standard polyesterautoclave and the system was purged six times with nitrogen, allowingthe pressure to rise to 150 p.s.i.g., and then releasing it slowly toatmospheric pressure each time.

Heat was then applied to the closed system, and when the temperatureinside the autoclave had reached 100 to 125 C., the stirrer was started.When the temperature of the outside wall of the autoclave had reachedabout 250 C. (the inside temperature being about 230 to 235 C. and thepressure being about 25 p.s.i.g.), the off-vapor valve was adjusted tomaintain these conditions of temperature and pressure. As the firstdistillate containing water and some ethylene glycol appeared, theesterification stage was considered to have started. The stirrer speedwas set up at 240 r.p.m. This esterification step usually took fromabout 40 to 60 minutes for completion, after which the pressure of thesystem was adjusted to atmospheric pressure. The heating rate was thenincreased until the temperature reached about 280 C. During this time,excess ethylene glycol was distilled off. An ethylene glycol slurry oftitanium dioxide was introduced through an injection port when theinside temperature had reached about 260 to 265 C. Then the insidetemperature was raised to about 280 C., the pressure was maintained atless than 2 mm. Hg. and the polymerization continued until a polymerhaving a specific viscosity in the fiber-forming range between 0.30 toless than about 0.4 was formed. The polymer was extruded through aspinnerette, and the filaments obtained were drawn about five timestheir original length over a hot pin at about 80 C.

The dyeing test used in Examples 1-8 was as follows: Fiber samples ofabout 3 denier were scoured and dried. One-half gram of fiber and 20 ml.of dye solution were placed in a small glass tube capable ofwithstanding internal pressure. The dye solution was prepared by mixing250 mg. of a disperse dye and 0.5 gram of a commercial dispersing agentin a 250 ml. volu- O.D. blank-O.D. sample X metric flask together withan amount of deionized water sufficient to fill the flask to the mark.The dye tubes were placed in a rotating rack held within a steam bath,and rotated for two hours at a temperature of about 210 F. The tubeswere then quickly quenched in ice, and 5 ml. aliquots were pipeted into50 ml. volumetric flasks which were then filled with dimethylformamide.The optical density of each solution was measured in a 1 cm. cell at thedominant wavelength of the dye. A blank tube (dye only) was alsoprepared and its optical density measured in the same way. The percentdye uptake on weight of the fiber (o.w.f.) was calculated using thefollowing equation:

original dye concentration (percent) percent dye blank uptake (whereO.D.:optical density) During the processing of polyester filaments,staple, blends, fabric, and the like, heating at various temperaturesfor various periods of time is often necessary, e.g., polyester fabricsmay be subjected to temperatures of 175 C. or higher for periods of upto 10 minutes or more. The following thermal stability tests were runwhere indicated: A S-gram sample of the polyester was fluffed into aball, placed in an aluminum cup into which about 10 one-half-inch holeshad been punched, and the ball was heated for 10 minutes at 175 C. in acirculating-air oven, often with a thermocouple held at the center ofthe ball.

EXAMPLE 1 The autoclave was charged with 166 grams of terephthalic acid,440 ml. of ethylene glycol, 0.078 gram of lithium sulfate, 0.967 gram ofantimony tn'oxide, 0.20 gram of pentaerythn'tol, and 10 grams ofmethoxypolyethylene glycol having an average molecular weight of about550. Polymer and fiber were prepared following the procedure describedabove.

The fiber took up 2.2 percent o.w.f. of Latyl Brilliant Blue 20 dye(C.l. Disperse Blue 61). Unmodified polyethylene terephthalate took up0.6 percent o.w.f. of this dye.

The fiber fused severely when heated at 175 C. for 10 minutes, thethermocouple within the carded ball recording at a temperature of 220 C.

EXAMPLES 2-8 Example 2 The autoclave was charged with grams terephthalicacid, 330 ml. ethylene glycol, 0.04 grams lithium acetate, 0.1 gramantimony glycoloxide, 0.3 gram pentaerythrito], and 8.0 grams of thereaction product of 4 molar equivalents of ethylene oxide with anapproximately equimolar mixture of straight chain alcohols having 14 to15 carbon atoms. Polymer and fiber were prepared following the proceduredescribed in Example 1. Examples 3-8 were conducted in the same manneras Example 2 with the exception that the amounts of pentaerythritol usedin each example were as follows: Example 3 0.15 grams; Example 4 0.2grams; and Example 8 0.00 grams. The alkoxy poly(oxyalkylene) glycolsused had the general formula: RO[C1-1 CH O],l-l for which the number ofcarbon atoms in the alkyl group R and the degree of polymerization ofethylene oxide (x) are shown in Table II. The resulting percent dyeuptake is shown for each sample.

The above results further substantiate the data shown in FIGS. l-3 andestablish the relationship between R and x which is theorized above.Example 4 was tested for heat stability and resisted fusion when heatedat C. for 10 minutes.

The Xenon-Arc lamp exposure used in Examples 9-12 was as described inAATCC 16E-196. Reflectance readings of undyed substrates were generallyin accordance with AATCC 110-1964.

EXAMPLE 9 The specified procedure was followed except that no glycoladditive and no manganese was used in the run. The autoclave was chargedwith 166 grams of terephthalic acid, 400 milliliters of ethylene glycol,0.078 gram of lithium sulfate, 0.967 gram of antimony trioxide, and 0.20gram of pentaerythritol. Knit tubings were prepared from the filaments(3 denier) and given a Varsol scour, then disperse dyed with various dyecombinations to six different shades shown at Table 111. The shades wereconsidered typical; two being light, two being medium, and two beingheavy. Tubings were then exposed to the Xenon-Arc Fade-Ometer for 20, 40and 80 SFl-l. The undyed tubings were exposed for 20 and 40 SFH.

EXAMPLE l Tubings were prepared as described in Example 9, except thatthe charge included a glycol additive having the formula: RO[G-O],l-l, Rbeing an alkyl group containing an average of 14-15 carbon atoms, Gbeing an ethylene radical, and at being about 14. The alkoxy glycoladditive was present in an amount of 1.2 mole percent.

EXAMPLE 11 The same procedure was followed as in Example 10, except that50 parts per million, based on the weight of the acid and glycol, ofmanganese ion in the form of manganese acetate was added to the charge.

EXAMPLE 12 The same procedure was used as in Example 10, except that 100parts per million of manganese ion in the form of manganese acetate wasincluded in the charge.

EXAMPLE 13 The same procedure as in Example was used, except that 100parts per million of manganous ion in the form of manganese acetate, and100 parts per million of 4,4 butylidenebis( G-t-butyl-m-cresol), wasincluded in the charge.

EXAMPLE 14 The procedure of Example 10 was followed, except that 100parts per million of 4, 4' butylidenebis(6-t-butyl-m-cresol) wasincluded in the charge. The manganese ion was not included.

TABLE III Dyed Lightfastness Xenon-Arc Fade-Ometer Example SFH 4O SFH 80SFH Beige 9 4 lt. 3-4 lt. 3 lt. 10 3-4 lt. 3 lt. 2 1t. 1 l 4 It. 3-4 It2-3 lt. 12 4 lt. 3 lt. 2-3 lt. 13 4 lt. 4 lt. 3-4 lt. l4 4 lt. 3-4 It 3It. Light Blue 9 4 lt. 3-4 lt. 3-4 It 10 3 lt. 2 lt. l-2 1t 1 1 4 lt.3-4 lt. 3 lt. 12 3-4 lt. 3 lt. 2-3 1t 13 4 lt. 3-4 It 3 It. 14 3 1t. 2-3lt. 2 It. Moss Green 9 3-41t 2-3 It 2 lt. 10 3 lt. 2-3 1t 2 It. 1 1 4lt. 3-4 It 2-3 lt. l2 4 lt. 3 lt. 2 lt. 13 3-4 It 2-3 lt. 2 1t. 14 3-4It 2-3 It. 2 lt. Gold 9 3-4 It 3 lt. 2-3 It. 10 3-4 It 3-4 It. 2-3 1t. 11 3-4 It 3 lt. 2-3 It. 12 4 lt. 3-4 lt. 2-3 lt. 13 3-4 1t 3 1t. 2-3 It14 3-4 1t. 3 lt. 2-3 lt.

Olive 9 4 lt. 4 lt. 3-4 lt. 10 4 lt. 3-4 lt. 3 lt. 11 3-41t. 3-4 lt. 3-4lt. 12 4 lt. 3-4 It. 3-4 It. 13 4 lt. 3-4 It 3-4 It 14 4 1t. 3-4 It. 31t. Navy 9 41t. 3-4 lt. 3 ll. 10 4 lt. 3-4 lt. 3-4 lt. rd. 11 4 lt. 3-4It. 3-4 lt. rd. [2 3-4 d1 3-4 dl. 3-4 dl. l3 4 lt. 3-4 lt. rd. 3-4 lt.14 3-4 It 3-4 It. rd. 3-4 lt.

lt. =light dl.= dull rd.= red TABLE IV Undyed Lightfastness Color-EyeReflectometer A Values Example lightness Purity DWL A Y A. P Unexposed YExposed 20 SFH Exposed 40 SFH Example 10 (Table III) shows the inherentinferior dyed lightfastness of the modified polyester. Examples 11 and12 show how this inherently poor dyed lightfastness is improved tonearly that of the substantially unmodified polyester. The dyedlightfastness of the sample containing 100 parts per million of themanganese ion retained not less than above 3.8 at 20 SFI-l, 3.2 at 40SFH, and 2.7 at SFH according to average Gray Scale values. Bycomparison, the dyed lightfastness of the sample containing both themanganese ion and the hindered phenol retained not less than about 3.8at 20 SFH, 3.3 at 40 SFH, and 3.0 at 80 SFH. This improvement, it willbe noted, lies primarily in the light color ranges, and at the higherSFH exposures. In the medium color ranges there was little or noimprovement, and in the case of moss green and gold, the figures show aslight loss in dyed lightfastness over the sample containing themanganous ion. This slight loss, however, is more than compensated bythe improvement shown with lighter colors, and the fact that even withmoss green and gold, there is no loss of dyed lightfastness at thehigher SFH exposures. The undyed lightfastness values of Table IV showcomparable whiteness retention in the undyed fibers.

It is to be understood the changes and variations may be made in thepresent invention without departing from the sphere and scope thereof asdefined in the appended claims.

We claim:

1. A disperse dyeable thermally stable linear condensation polyesterhaving inherent dyed lightfastness qualities, consisting of at least 85percent by weight of the polyester of terephthalic acid and a dihydricalcohol selected from the group consisting of glycols of the seriesHO(CH )nOl-!, in which n is an integer from 2 to 10, andcyclohexanedimethanol modified with about 0.25-3 mole percent, based onthe weight of the acid, of a chain terminating compound having thegeneral formula: RO[GO],H, where R is an alkyl group containing 8-20carbon atoms; G is a hydrocarbon radical selected from the groupconsisting of ethylene, propylene and isomers thereof, and butylene andisomers thereof, and x is an integer having a value of from 8-20, and isabout equal to or greater than the number of carbon atoms in R; andincluding about 10-500 parts per million, based on the weight of theacid and glycol, of manganous ion, and 50-150 parts per million of ahindered phenol selected from the group consisting of 4,4-butylidenebis(6-t-butyl-mcresol) and 2,2'-butylidenebis (o-t-butyl-m-cresol).

2. The new composition of matter defined in claim 1 wherein thesynthetic linear condensation polyester is prepared from terephthalicacid and ethylene glycol, and further modified with up to about 0.45mole percent, based on the amount of the terephthalic acid, of atetra-functional chain-branching agent.

3. The new composition of matter defined in claim 2 wherein thechain-branching agent is pentaerythritol.

4. The new composition of matter defined in claim 1 wherein thesynthetic linear condensation polyester is prepared from terephthalicacid and ethylene glycol, and further modified with up to about 0.7 molepercent, based on the weight of the terephthalic acid, of atri-functional chainbranching agent.

5. The new composition of matter defined in claim 4 wherein thechain-branching agent is tn'mesic acid.

6. The new composition of matter defined in claim 2 wherein thechain-branching agent is pentaerythritol, in an amount of about 0.2 molepercent, based on the weight of terephthalic acid.

7. The new composition of matter defined in claim 4 wherein thechain-branching agent is trimesic acid in an amount of about 0.5 molepercent, based on the weight of the terephthalic acid.

8. The new composition of matter defined in claim 1 wherein the additivehaving the typical general formula R- O[GO],-H is present in from about0.75 to 2 mole percent, based on each polyester repeating unit, R is analkyl group containing an average of l2-l6 carbon atoms, G is anethylene radical, and x has a value of 14.

9. A fiber formed from the composition of claim 1.

2. The new composition of matter defined in claim 1 wherein thesynthetic linear condensation polyester is prepared from terephthalicacid and ethylene glycol, and further modified with up to about 0.45mole percent, based on the amount of the terephthalic acid, of atetra-functional chain-branching agent.
 3. The new composition of matterdefined in claim 2 wherein the chain-branching agent is pentaerythritol.4. The new composition of matter defined in claim 1 wherein thesynthetic linear condensation polyester is prepared from terephthalicacid and ethylene glycol, and further modified with up to about 0.7 molepercent, based on the weight of the terephthalic acid, of atri-functional chain-branching agent.
 5. The new composition of matterdefined in claim 4 wherein the chain-branching agent is trimesic acid.6. The new composition of matter defined in claim 2 wherein thechain-branching agent is pentaerythritol, in an amount of about 0.2 molepercent, based on the weight of terephthalic acid.
 7. The newcomposition of matter defined in claim 4 wherein the chain-branchingagent is trimesic acid in an amount of about 0.5 mole percent, based onthe weight of the terephthalic acid.
 8. The new composition of matterdefined in claim 1 wherein the additive having the typical generalformula R-O(G-O)x-H is present in from about 0.75 to 2 mole percent,based on each polyester repeating unit, R is an alkyl group containingan average of 12-16 carbon atoms, G is an ethylene radical, and x has avalue of
 14. 9. A fiber formed from the composition of claim 1.